Chapter 2 Configuration and Installation
SCXI-1121 User Manual 2-16 www.natinst.com
When connecting or disconnecting signal lines to the SCXI terminal block screw terminals,
make sure the lines are powered off. Potential differences between the lines and the SCXI
ground create a shock hazard while you connect the lines.
Connect the signal wires to the screw terminals by inserting the stripped end of the wire
fully into the terminals. Tighten the terminals to a torque of 5 to 7 in.-lb.
Connections, including power signals to ground and vice versa, that exceed any of the
maximum signal ratings on the SCXI device can create a shock or fire hazard or can
damage any or all of the boards connected to the SCXI chassis, the host computer, and the
SCXI device. National Instruments is not liable for any damages or injuries resulting from
incorrect signal connections.
If high voltages (≥30 Vrms and 42.4 V peak or 60V DC) are present, you must connect a
safety earth ground wire to the terminal block safety ground solder lug. This complies with
safety agency requirements and protects against electric shock when the terminal block is
not connected to the chassis. To connect the safety earth ground to the safety ground solder
lug, run an earth ground wire in the cable from the signal source to the terminal block.
National Instruments is not liable for any damages or injuries resulting from inadequate
safety earth ground connections.
Do not loosen or re-orient the safety ground solder lug hardware when connecting the
safety ground wire. To do so reduces the safety isolation between the high voltage and
safety ground.
Clean devices and terminal blocks by brushing off light dust with a soft, nonmetallic brush.
Remove other contaminants with deionized water and a stiff nonmetallic brush. The unit
must be completely dry and free from contaminants before returning to service.
Use only National Instruments TBX Series cable assemblies with high-voltage TBX Series
terminal blocks.
Front Connector
Figure 2-3 shows the pin assignments for the SCXI-1121 front connector.